We have prepared nanoporous SnO2 hollow microspheres (HMS) by employing the resorcinol-formaldehyde (RF) gel method. Further, we have investigated the electrochemical property of SnO2-HMS as negative electrode material in rechargeable Li-ion batteries by employing three different binders-polyvinylidene difluoride (PVDF), Na salt of carboxy methyl cellulose (Na-CMC), and Na-alginate. At 1C rate, SnO2 electrode with Na-alginate binder exhibits discharge capacity of 800 mA h g(-1), higher than when Na-CMC (605 mA h g(-1)) and PVDF (571 mA h g(-1)) are used as binders. After 50 cycles, observed discharge capacities were 725 mA h g(-1), 495 mA h g(-1), and 47 mA h g(-1), respectively, for electrodes with Na-alginate, Na-CMC, and PVDF binders that amounts to a capacity retention of 92%, 82%, and 8% . Electrochemical impedance spectroscopy (EIS) results confirm that the SnO2 electrode with Na-alginate as binder had much lower charge transfer resistance than the electrode with Na-CMC and PVDF binders. The superior electrochemical property of the SnO2 electrode containing Na-alginate can be attributed to the cumulative effects arising from integration of nanoarchitecture with a suitable binder; the hierarchical porous structure would accommodate large volume changes during the Li interaclation-deintercalation process, and the Na-alginate binder provides a stronger adhesion betweeen electrode film and current collector.

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Tin oxide-carbon composite porous nanofibres exhibiting superior electrochemical performance as lithium ion battery (LIB) anode have been prepared using electrospinning technique. Surface morphology and structural characterizations of the composite material is carried out by techniques such as XRD, FESEM, HR-TEM, XPS, TGA and Raman spectroscopy. FESEM and TEM studies reveal that nanofibers have a uniform diameter of 150-180 nm and contain highly porous outer wall. The carbon content is limited to *10% in the nanofibers as shown by the TGA and EDAX which does not fade the high capacity of SnO 2 . These nanofibers delivered a higher discharge capacity of 722 mAh/g even after 100 cycles at high rate of 1C. The excellent electrochemical performance can be ascribed to the synergy effect of small amount of carbon in the composite and the hierarchically porous structure which accommodate large volume changes associated with Li-ion insertion-desertion. The porous nano-architecture would also provide a short diffusion path for Li ? ions in addition to facilitating high flux of electrolyte percolation through micropores. The electrochemical performance of composite material has also been tested at 60°C at a higher rate of 2C and 5C. Post cycling FESEM analysis shows no volumetric and morphology changes in porous nanofibers after completing rate capability at high rate of 10C.

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A new, rapid, and cost-effective method for synthesizing hollow microspheres (HMSs) of cobalt oxide (Co 3 O 4 ) using the phloroglucinol–formaldehyde gel route is reported here. Further, the synthesized hollow Co 3 O 4 microspheres were investigated as an anode material for Li-ion batteries. The Co 3 O 4 hollow spheres exhibited excellent electrochemical performance and cycling stability, for example, a capacity of 915 mA h g –1 was obtained at 1 C rate over 350 cycles. The material also exhibited good performance at high rates, viz., capacities of 500, 350, and 250 mA h g –1 at 10 C, 25 C, and 50 C, respectively, with good capacity retention over 500 cycles. The excellent electrochemical performance of Co 3 O 4 can be ascribed to the porous nanoarchitecture that provides a short diffusion length for Li + ions and high electrolyte percolation in the porous structure. Additionally, the thin porous wall of the nanocages provides an effective way to overcome the issues associated with the volume change occurring during Li charge/discharge. The conversion of Co 3 O 4 into Co upon discharge was also probed by measuring the magnetic properties.

Though the Li−S battery is considered as an attractive next-generation battery technology, a few challenges still need to be solved, for example, poor conductivity of the electrode, sluggish reaction kinetics, polysulfide shuttling, and cycle life. Here, we design an effective polysulfide immobilizer by grafting nitrogen-doped carbon nanotubes (NCNTs) on hollow Co 3 O 4 microspheres and use it to prepare a freestanding sulfur composite cathode. This architecture imparts benefits such as superior electronic conductivity, better buffering of volume changes during electrochemical cycling, high polar surface for polysulfide absorption, and outstanding electrocatalytic activity to ameliorate the lithium polysulfide conversion kinetics. As a result, the composite sulfur electrode shows an initial capacity of 1104 mAh g −1 (at 0.5C rate) and capacity retention of 73% after 300 cycles. Similarly, at a 1C rate, the electrode shows stable cycling behavior over 800 cycles with a capacity retention of 65%. The Li−S cell also exhibits high power capability, as at a 5C rate, it delivers a capacity of 385 mAh g −1 . The synergistic effect between the polysulfide adsorbing additives Co 3 O 4 and NCNT plays a major role in the high utilization of sulfur even when sulfur loading increases to 12 mg cm −2 .

Polyacrylonitrile co methyl methacrylate (PAN co‐MMA) based nanofibers were synthesized by electrospinning technique and were converted into carbon nanofibers (CNFs) by heating at 1000°C (PAN‐1000), 1800°C (PAN‐1800), and 2200°C (PAN‐2200). Various characterizations such as SEM, TEM, Raman, FT‐IR have been carried out to study the effect of heat temperature on the microstructure of carbon fibers. The carbon nanofiber diameter varies in the range 600‐120 nm for different heat temperatures. Further, these CNFs were evaluated as freestanding anode in Li‐ion batteries. The PAN‐1000 and PAN‐1800 CNFs show stable capacity up to 150 cycles and specific capacity of 254 and 238 mAh g−1 at high discharge rate of 1C; however PAN‐2200 despite of better microstructure and surface area (~60m2/g) shows low specific capacity of 105 mAh g−1mAh/g, that is probably due to distribution of pore structures present in fibers as well as low electrolyte wetting through the carbon fibers electrode observed in post‐cycling SEM analysis. In addition, at higher discharge rate of 3C, PAN‐1000 shows stable cyclability and high capacity of 198 mAh g−1 over 450 cycles and 238 mAh g−1at 1C rate over 500 cycles. The microstructure and pore structure all affect the energy storage performance of PAN‐co MMA based CNFs.

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